Hemp
hits its stride

Claire
Cockcroft, The Guardian, May 10, 2001

The
cousin of cannabis is perfect for an industry looking for greener resources, says
Claire Cockcroft

It
is green, high in fibre, improves strength and reduces weight. This is not the
perfect diet but an ingredient for the car industry. Hemp, once an outcast in
agricultural circles, is making a comeback and cropping up in unconventional places.

It
has been heralded as the environmentally friendly raw material for many consumer
needs, including composites for the automotive industry, in a move towards the
widespread production of greener, recyclable car parts. Cannabis sativa, to use
hemp's official name, has been harvested for millennia for the strong and extremely
long coarse fibres in the stem, and its valuable seed oil. It has been used to
make ropes, textiles and paper, and fragments of hemp fabric dating from 8,000
BC have been unearthed.

Hemp
production prospered during both world wars but was then rejected in favour of
cheaper synthetic fibres. Although often confused with marijuana, hemp is a distinct
variety within the species: over the years, plant breeders have cultivated hemp
varieties with increased stem fibre content and very low levels of delta 9-tetrahydro-cannabinol
(THC), the psychoactive ingredient of its controversial cousin. Several countries
have legalised hemp farming, some even using it to manufacture currency paper.
Plants in Poland are used to make hemp particle board, private plots in Japan
provide material for the Emperor's religious robes.

Hemp produces more pulp per acre than timber and is a sustainable alternative
for the paper industry. Since it is low in lignin, a natural strengthening agent
in plant cells, and is naturally a creamy colour, it requires fewer environmentally
damaging chemical treatments, like bleaching, during paper production. Plant-based
composites have been widely used in construction: the ancient Egyptians used straw
to reinforce clay walls and wattle and daub was used in medieval times. With the
rise of more durable construction materials, plant fibres were left in the lurch.

Now,
they are being recognised as a valuable alternative for the composites industry.
About four billion tons of hemp, flax, jute or kenaf are grown globally, representing
a vast sustainable and renewable raw resource that has a lower impact on the environment
than fibreglass and plastic. These "bast" fibres have a better stiffness per unit
weight and outstanding intrinsic mechanical properties, consisting of about 85%
cellulose and hemicellulose, which gives enormous tensile strength, and 15% lignin
and pectin. They have excellent heat, sound and insulating properties, good chemical
reactivity for processing and even anti-microbial and anti-mildew properties -
a built-in pesticide system.

Last
year, the ministry of agriculture commissioned a report on natural fibres in the
automotive industry. At a meeting of the alternative crops technology interactive
network (Actin) Joe Ellison, of the Textile Consultancy, reported that of the
50 million vehicles made globally, up to 20kg of natural fibres could be used
to make parts including dashboards, door panels and parcel shelves per vehicle.
Germany is the driving force, responsible for more than two-thirds of European
production of natural fibre composites with the car manufacturers Mercedes (Daimler/Chrysler),
BMW and Audi/Volkswagen leading the way.

Following
the introduction of jute-based door panels in the Mercedes E class five years
ago, fibre usage in the German car industry has soared from 4,000 tons in 1996
to 15,500 tons in 1999 and consumption is predicted to double over the next five
years. The door trim panels for the Daimler/Chrysler Sebring convertible are made
from Eco-Cor, a biocomposite plastic made of 25% hemp, 25% kenaf and 50% polypropylene.
The blend is formulated for fire-resistance and is "self-extinguishing".

Not only
are plant-based fibres usually cheaper to process and more environmentally friendly
than glass-fibre and plastic alternatives, which are tricky to dispose of, they
often have superior technical properties. They are less prone to splintering and
save weight by as much as 30%, improving fuel consumption. With market prices
of 30-35p/kg, compared to 85-90p/kg for plastics or £5.50/kg for fibreglass, natural
fibre composites present a cheaper alternative that can also be recycled. EC legislation
now demands that manufacturers reduce the environmental impacts of vehicles. Ian
Bartle, the chief executive of Actin, says:

"With
the new 'end of life' vehicle (ELV) regulations, car manufacturers can no longer
be complacent about the life cycle of their product, since they are now responsible
for the envi ronmentally sound disposal of their creation." Hemcore Ltd was founded
in 1993 when grain mountains were getting higher and farmers were on the look-out
for alternative land uses. With the volatility in the wheat market, finding a
viable alternative crop was critical.

Based in Essex, Hemcore is the only hemp producer in the UK. According to its
managing director, Ian Low, hemp provides an excellent break in cereal rotation
as it can be grown organically. It also cleans the ground: its quick growth suppresses
weed competition, its deep roots improve soil structure and fewer pests and diseases
afflict the following wheat crops because of its anti-fungal and anti-microbial
properties.


Dr Claire Cockcroft is at the Institute of Biotechnology in Cambridge